An electrophoretic display is a device based on the electrophoresis phenomenon of charged pigment particles dispersed in a solvent. The display usually comprises two electrode plates placed opposite of each other and a display fluid comprising charged pigment particles dispersed in a solvent is sandwiched between the two electrode plates. When a voltage difference is imposed between the two electrode plates, the charged pigment particles may migrate to one side or the other, depending on the polarity of the voltage difference, to cause either the color of the pigment particles or the color of the solvent to be seen from the viewing side of the display.
Alternatively, an electrophoretic dispersion may have two types of pigment particles of contrasting colors and carrying opposite charges, and the two types of pigment particles are dispersed in a clear solvent or solvent mixture. In this case, when a voltage difference is imposed between the two electrode plates, the two types of pigment particles would move to the opposite ends (top or bottom) in a display cell. Thus one of the colors of the two types of the pigment particles would be seen at the viewing side of the display cell.
The method employed to drive an electrophoretic display has a significant impact on the performance of the display, especially the quality of the images displayed.
Shutter mode driving involves moving the charged pigment particles laterally to the sides to expose the color of a background layer. However, in practice, it is difficult to clear the particles gathered on a driving electrode. This is because the horizontal electrical field in the center area of the driving electrodes is low. A horizontal electrical field only exists at the edge areas of the neighboring driving electrodes.